The foundations of offshore constructions are becoming more and more important. This is particularly true for so-called offshore wind turbines which are often grouped together in so-called open-sea wind farms. Such offshore locations offer numerous advantages, for example constant wind conditions and above-average wind speeds.
As a result of these conditions, but also the dead weight acting on the offshore construction, and the flow of water, particular requirements for the underwater construction of the offshore construction are, however, also necessary in order to ensure structural stability. Various foundation options for such offshore constructions are known from the prior art for this purpose. As well as flat foundations, and gravity foundations, monopile foundations (1 pile), tripod or tripile foundations (3 piles in each case), and jacket foundations (4 piles) are in particular known.
In the case of pile foundations, one or more foundation piles are usually driven or wash-drilled into the sea bed. These piles often take the form of hollow steel piles which are placed in the sea bed over a predetermined length. The underwater structure or the anchoring structure of the offshore construction, for example in the form of a jacket foundation, is then placed on these piles.
After this, the cavities which result hereby, in particular annular cavities, are usually filled with a hardening, especially hydraulically setting grout. Cement-based high-performance concrete or high-viscosity polymer concretes are, for example, used as grout which, after they have hardened, transmit forces between the parts of the components which surround each other.
An underwater structure of an offshore construction, and a foundation method are known, for example, from WO 2011/010937 A1.
A disadvantage of the above described foundation of underwater constructions is that, when the grout is poured into the cavities which are arranged under water when the pouring takes place (and hence are initially full of water), the grout can bleed/be washed out, wherein constituents of the grout are released into the surrounding water and leak from the inside of the underwater construction. This leaking is intensified by the grout poured into the cavity displacing the water situated therein. This has the consequence, inter alia, of it being more difficult to monitor the filling process (grouting) because the cement slurry which leaks into the surrounding sea water from the inside of the underwater construction significantly impairs the visibility.
A further disadvantageous consequence of the above described foundation of underwater constructions is that the grout often overflows in an uncontrolled manner, inter alia because it is more difficult to monitor the process and owing to the impaired visibility. Grout hereby leaks, for example, at an upper opening of the filled cavity because it has not been possible to monitor sufficiently the fill level of the grout inside the cavity and therefore an excessively large amount of grout has been pumped into the cavity.